[Kagayaki]

Originally Posted by YoakeNoHikari

Explained in light novel.

Spoiler for Excerpt, already covered in anime.:

"......In Butei High, there is a rule concerning gunfire. The rule is "Don't fire more than you need to," which means, you can shoot as much as you like. However, most of the students here are Butei that are desensitized to gunfire, since it is part of their daily routine. But, although it's like that..."

Firing a gun during the introductions of the new semester, she's got to be the first one.

It's not a matter of being desensitized to gunfire, and it doesn't matter whether or not it's legal. It's a matter of firing in a way in which you could easily hit other students. Believe it or not, in the real world, carrying a gun comes with a certain amount of responsibility, and Aria is clearly not mature enough for that. It's not like the Butei are so superhuman that they can just shrug off getting hit by a stray bullet.

The fact is that firing a gun like that in a crowded space for no apparent purpose is flat out immoral, and it doesn't make any sense why the school administration would be ok with that.